During the use of a cell phone, a SIM (Subscriber Identity Module, subscriber identity module) card needs to be registered first, and then a communication function of the cell phone can be used. After the cell phone enters a region where no signal coverage exists or signal quality is poor, for example, a subway, an elevator, or a basement, the problem that the registration of the SIM card of the cell phone fails occurs. If the reason of the failure is that the network considers the SIM card to be illegal, network residence cannot be restored even through manual network search, and a user must turn off the cell phone manually and restart a whole machine of the cell phone to restore a network connection.
In the prior art, the SIM card can be re-registered only by powering off the cell phone and then restarting the whole machine of the cell phone, so that the SIM card re-accesses the network. However, as smart phones are popular and more and more application programs in the smart phone exist, it takes a long time to power down and restart the smart phone, and if the user is using an application program of the smart phone, the restart after the turn-off affects the experience for the user to use the cell phone.